// 易错点3：必须先判断stack2.length0，再访问stack2.at(-1)（避免栈空时取到undefined）
But the British Medical Association said the government was at risk of creating unrealistic expectations given how stretched GP services already were.
。雷电模拟器官方版本下载对此有专业解读
优化：随机选基准避免最坏情况 O(n²)
Trial launched to 'help spot health risks early'